Saadia ben Joseph was born in the village of Dilaz in the Fayyum region of Egypt. He left Egypt in about 905 and for several years wandered between Palestine, Syria, and Baghdad. In 928, despite his foreign origin, he was appointed Gaon of the academy of Sura.

Saadia wrote his great philosophical classic, The Book of Doctrines and Beliefs, during the years he was suspended from office and placed under arrest by David ben Zaccai, the Exilarch ("resh geluta"), because he refused ben Zaccai's order to sign a document that he considered unjust.

Saadia's view was that the Torah conformed entirely with reason. God simply revealed the knowledge of the Torah through prophets as a special act of compassion, so that knowledge of the Torah should be available to all, even those who lacked the philosophical sophistication or the time to discover it for themselves.

Saadia is also well known for his refutations of the Karaite sect of Judaism.